This disclosure relates to a transistor switch that maintains a substantially constant on resistance when passing an input signal that includes a variable voltage component (e.g., an alternating current (AC) component).
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Many integrated circuits use switches formed using transistors to allow a signal to pass through the switch to be received by other circuitry. Generally speaking, the lower the amount of signal distortion in the circuitry of an electronic device, the greater the reliability of the circuitry. On an electronic display panel, for example, thin film transistors may switch a variety of input signals to operate the display. In general, these signals include substantially only a direct current component. When the transistor switches are used to pass only direct current input signals, the transistor switches may keep a substantially constant “on resistance,” or RON, which is the resistance of the transistor switch when the transistor switch is on. By maintaining a substantially on resistance RON, the transistor switches generally may not distort these direct current input signals.
The on resistance RON of transistor switches may vary, however, when the input signals include a variable voltage component that varies over time. When the input signals include a sinusoidal or other alternating current component, the on resistance RON of the transistor switches may vary over time. The resulting output signals may be non-linear, unreliable, and/or high in noise. Moreover, transistors formed as circuit-on-glass devices made from polysilicon may exhibit even greater variability of on resistance RON. As a result, sending a signal that includes a variable voltage component through a transistor switch—particularly one formed as a circuit-on-glass device—may produce an unreliable output signal. Although increasing a size of the transistor may reduce the variability of the on resistance RON, a larger transistor takes up more integrated circuit die space. The comparatively larger size of the transistor may crowd out other possible circuitry on the integrated circuit die and/or may add to the design cost. A larger transistor may also consume more energy, lowering the potential battery life of electronic devices that would include the larger transistor. Moreover, given design constraints, making a transistor that is large enough to completely eliminate the on resistance RON variability may be difficult or impractical.